390
Armstrong Siddeley Viper ASV.S turbojet. Seven-stage compressor, annular combustionchamber With vaporiiing burners and single-stage turbine. Mass flow, 30 Ib/sec; pressure ratio,
3.5:1. Overall diameter, 24.7in; length, as shown in drawing, 65.4in; dry weight, including oil tank,two ignition units, and Graviner spray ring, 515 Ib. Maximum thrust, 1,640 jb at 13,400 r.p.m.
with specific fuel consumption of 1.0* Ib/hr/lb.
FLIGHT, 2 September 1955
Viper. Originally, the Viper was intended »be a cheap turbojet for expendable applications
and the design was accordingly simplified to thisend. The first production engine was the ASV.3,
which has been built in large numbers at thedesign rating of 1,640 lb thrust and has been
shipped to Australia for installation in the Jindi-vik 2 target aircraft. In this form the Viper has
a simplified fuel system and the minimum num-ber of accessories, starting being carried out by
an external source of shaft power applied to asocket on the engine.
Early development running established so gooda life that a new requirement was written around
the Viper for the development of an engine suit-able for the propulsion of manned aircraft. The
first engine of this range is the ASV.S, at thesame rating as the 3 but fully equipped with all
normal accessories and with no compromisesmade in choice of material. As the Viper 101,
such engines are being used in the Jet Provost,the transonic Midge prototype and the supersonic
French Trident. Behaviour of these engines atvery high altitudes has now been explored with
a unit mounted under the starboard wing of aCanberra.
An afterburning Viper first ran over a year ago.Designated ASV.7R, this engine is based on tike
5 and gives 2,470 lb thrust. Such an engine isalso being developed in France by Avions Marcel
Dassault, who hold a manufacturing licence forthe Viper and have now started production of an
engine designated MD.30. In Britain an up-rated Viper 5, styled ASV.8, has been run at
1,750 lb thrust. The ASV.10, listed in the datatable on page 407, does not yet exist. This engine
will fit die same frame as do its predecessorsbut it will have a greater mass flow and be sig-
nificantly more powerful.
Armetrong Siddeley Snorter. Dimensions: chamber length, 2S.4in to end of mounting cone;nozzle diameter, 5.41 in; throat area, 5.21 sq in; characteristic length, Win. Weight: gearbox,
drive and pumps, about 77 Ib; valves, filters, bottles and electric gear, about 57 Ib; chamber andmounting, igniter, valves and electrical gear, about 79 Ib; total, approximately 213 Ib. Note:
according to th* S.B.A.C. definition of a motor the Snorter's dry weight would be about 166 Ib.Performance: full thruit, about 2,000 Ib at sea level, rising with altitude. Specific impulse, 195
maximum at sea level; maximum combustion chamber pressure, 300 Ib/sq in; maximum combustiontemperature, approximately 2,650 deg K; jet velocity, 6,270ft/sec.
Aircraft Rockets. The Armstrong Siddeleycompany were pioneers of liquid-oxygen aircraft
rocket motors. In fact, the company's Snarler,illustrated alongside, was the first unit incorpor-
ating a pump-fed liquid oxygen supply ever to bedesigned and flown in a manned aircraft.
Designed as a booster unit for fighters to givea sea-level thrust of 2,000 lb (and rather more at
altitude) the Snarler ran on liquid oxygen and a65/35 per cent mixture of water and methanol.
These propellants were supplied at high pressureby centrifugal pumps, the liquid oxygen being
injected directly into the head of the combustionchamber and die water-methanol mixture being
passed through a regenerative cooling jacket sur-rounding the combustion chamber itself, final
entry to the combustion chamber being madethrough holes in the wall. The Snarler was test
flown in a Hawker Nene-powered fighter, dieturbojet being employed to drive die rocket pumps
through a mechanical gearbox. In die accom-panying photograph, die pumps, valves and com-
bustion chamber have been rearranged in morecompact form for display purposes. The valve-
group in the centre provided automatic controlto facilitate safe starting and to enable the unit to
be governed by a single lever in the cockpit.
Earlier this year die company announced dieexistence of a rocket motor with die name
Screamer. It was then stated that the propcllantsemployed were aviation turbine fuel in conjunc-
tion with an oxidant which, to judge by theinstallations at die company's rocket division at
Ansty, is likely to be liquid oxygen. The mechani-cal details of die Screamer are entirely withheld,
as are details of its progress, with the exceptionof one significant fact: the Screamer has already
completed a considerable amount of developmentrunning and the thrust obtained has exceeded the
design figure. It is highly likely that this designthrust is considerably greater man that for the
Snarler.